In the early 1970s, the architects Josef Paul Kleihues and Hardt-Waltherr Hämer shaped a concept called Kritische Rekonstruktion, critical reconstruction. Its aim is rarely an exact copy of what was lost. Usually it reproduces important features of the historic city structure. After reunification, Hans Stimmann, Berlin’s Senate building director from 1991 and again from December 1999 to October 2006, pressed for building in this sense. New buildings were to follow the historic street plan and the local building types. He was criticized several times. His critics said that his rules restricted architects too much. His supporters considered the strict rules necessary for a city like Berlin.